Here's Dorothy Rowe's take on the Depression debate. - Dorothy Rowe is a psychologist who has written several books about depression.

The true nature of depression - Dorothy Rowe's article in The Guardian

Extract:

"Gordon Parker makes the important point that depression is over-diagnosed because doctors do not discriminate between depression and unhappiness, but he fails to understand that the list of symptoms that psychiatrists use to diagnose the condition does not include the one distinguishing feature of depression which any person who has been depressed knows only too well. When we are unhappy, we can be close to and comforted by other people and we comfort ourselves, but when we are depressed, we are alone in a prison which seems as real as it is invisible. It is this terrible aloneness that makes depression far worse than any physical illness."